The following description relates to a laminated nozzle assembly having one or more thick plates.
A laminated nozzle assembly may be used to discharge a hot melt adhesive onto a substrate. The substrate may be, for example, a layer of material, such as a nonwoven fabric, or a strand of material, such as an elastic strand to be applied on an article. The article may be, for example, a disposable hygiene product. The laminated nozzle assembly may include one or more first discharge slots for discharging the hot melt adhesive and one or more second discharge slots configured to discharge air. The discharged air causes the discharged hot melt adhesive to oscillate or vacillate during application to the substrate.
FIG. 1 shows a partial exploded view of a conventional laminated nozzle assembly 10. Referring to FIG. 1, a conventional laminated nozzle assembly 10 includes a plurality of plates having internal conduits formed therein allowing flow of the hot melt adhesive and air therethrough. FIG. 2 is a plan view of the individual plates forming the conventional laminated nozzle assembly 10. Referring to FIGS. 1 and 2, the conventional laminated nozzle assembly may include eleven plates 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32 secured between a first end plate 34 and a second end plate 36. A first internal conduit 38 may be formed through a plurality of the plates for delivering the hot melt adhesive to a first discharge slot 40. The first internal conduit 38 is formed by a plurality of aligned openings in the plates. A second internal conduit 42 may also be formed through a plurality of the plates for delivering the air to a second discharge slot 44. The second internal conduit 42 is formed by a plurality of aligned openings in the plates.
FIG. 9a is an enlarged plan view of plates 20, 22, 24 of the conventional laminated nozzle assembly 10 of FIGS. 1 and 2. Referring to FIGS. 2 and 9a, plate 20 includes a plurality of first apertures 46. The first apertures 46 are disposed in the first internal conduit 38 and split the first internal conduit 38 into multiple flow paths for the first fluid. Similarly, plate 24 includes a plurality of second apertures 48. The second apertures 48 are disposed in the second internal conduit 42 and split the second internal conduit 42 into multiple flow paths for the second fluid. The first and second apertures 46, 48 are circular in shape, as shown in the plan view. Each first aperture 46 has an area of approximately 0.00031 in2, and each second aperture 48 also has an area of approximately 0.00031 in2.
With further reference to FIGS. 1, 2 and 9a, the nozzle plate 22 of the conventional nozzle assembly 10 includes a plurality of discharge assemblies 50. Each discharge assembly 50 includes a first discharge slot 40 and a pair of second discharge slots 44. The first discharge slot 40 and second discharge slots 44 each include an inlet end 52, 54 having a size and shape corresponding to the size and shape of the first and second apertures 46, 48. That is, the inlet end 52 of the first discharge slot 40 is circular in shape and is configured to receive the first fluid from the first aperture 46, and the inlet ends 54 of the second discharge slots 44 are circular in shape and configured to receive the second fluid from the second apertures 48. The inlet ends 52, 54 of the first and second discharge slots 40, 44 have a greater diameter or width than an adjacent intermediate portion 56, 58 of the respective first and second discharge slots 40, 44 to which the fluid flows.
The flow paths defined by the first and second internal conduits 38, 42 may be indirect, circuitous, or otherwise inhibit efficient flow of the fluids (i.e., the hot melt adhesive and/or the air) through the laminated nozzle assembly 10. For example, the flow path defined by the first internal conduit includes a number of stepwise changes in direction, extends laterally to locations near outer edges of the laminated plates and extends at these locations through numerous plates. In addition, the first and second apertures 46, 48 of the first and second internal conduits 38, 42 are small and restrict flow of the first and second fluids. In addition, the narrowing of the width or diameter between the inlet ends 52, 54 and respective intermediate portions 56, 58 of the first and second discharge slots 40, 44 may also restrict fluid flow.
Restricted fluid flow in the convention nozzle assembly 10 may cause a decrease in a velocity of the fluid in the nozzle assembly 10. In particular, the indirect, circuitous, or otherwise flow inhibiting characteristics of the flow path for the hot melt adhesive may cause a decrease in velocity and allow the hot melt adhesive to collect in various portions of the first internal conduit 38. The reduced velocity and collection of the hot melt adhesive may lead to plugging of the first conduit 38.
In addition, reduced velocity and/or fluid collection of the hot melt adhesive in the first internal conduit 38 may lead to cooling of the hot melt adhesive. In particular, with a reduced velocity, the hot melt adhesive requires a longer length of time to flow through the nozzle assembly 10. The hot melt adhesive is fed to the nozzle assembly at a desired temperature. However, upon flowing into the nozzle assembly 10, the hot melt adhesive may cool with time. Cooling of the hot melt adhesive may lead to increased viscosity, which may also inhibit flow through nozzle assembly 10 by reducing velocity and/or collecting in various portions of the first internal conduit 38.
Cooling of the fluids, and in particular, the hot melt adhesive, may also occur as result of prolonged exposure to a conduit wall near an edge region of the nozzle assembly 10. That is, in the conventional nozzle assembly 10, the first internal conduit may extend in a width direction to an area relatively close to an edge region of the plates. As such, ambient air, typically at a lower temperature than the hot melt adhesive, may cool the hot melt adhesive through the relatively thin edge region of the plates. Prolonged exposure to this lower-temperature edge region may result from a length of the flow path in this region, or a lower velocity of fluid in this region.
Moreover, when the chemistry and manufacturing of the discharged material (e.g., the adhesive) is not well controlled, particulate matter or contaminants, ash and/or other residue may be present in the material when introduced to the nozzle assembly 10, and charring may occur at what are otherwise normal operating temperatures. The existence of such particulate matter, contaminants, or the like may further exaggerate plugging of the conduits, for example, at the apertures 46, 48, discharge slots 40, 44 or other areas where flow is restricted and/or fluid velocity is reduced.
To this end, filter plates 16, 28 are included in the conventional laminated nozzle assembly 10. The filter plates 16, 28 include a plurality of filter openings 60, 62 and are disposed in respective flow paths defined by the first internal conduit 38 and second internal conduit 42. Accordingly, the filter plates 16, 28, and in particular, the filter openings 60, 62 may collect any particular matter, contaminants or other residue exceeding a predetermined size that is present in the fluids.
However, the filter plates 16, 28, disposed in respective first and second internal conduits 38, 42, even when clean, restrict flow of the fluids. As a result, the fluids, and in particular, the hot melt adhesive, may collect upstream from the filter plate 16 in the first internal conduit 38 and experience a decrease in velocity. These drawbacks are magnified as the filter plates 16, 28 collect the particulate matter, contaminants, or the like, from the fluids, since an area of the filter plates 16, 28 through which the fluid may flow is reduced.
In addition, with the indirect flow paths in the conventional laminated nozzle assembly 10, a dwell time, or time of the fluid to travel from an inlet of the laminated nozzle assembly 10 to discharge slots 40, 44 may be undesirably long. This may affect start/stop performance of the laminated nozzle assembly 10 by discharging fluid for an undesirable amount of time after shut off, or delaying discharge of fluid for an undesirable amount of time after starting the application device. In turn, an application pattern of the fluid, and in particular, start and stop locations, onto the substrate may not be precisely controlled.
Accordingly, it is desirable to provide a laminated nozzle assembly having an internal conduit or conduits allowing for increased passageway size, higher fluid velocity, and more direct flow paths to the discharge orifices.